1. Field of the Invention
The present invention relates to partially automated vehicular mechanical transmission systems of the type not having automatic master clutch controls and utilizing controlled engine fueling to cause substantially zero torque transfer conditions in the driveline for disengaging the jaw clutches associated with a gear ratio to be disengaged. In particular, the present invention relates to a robust, general-purpose engine fueling control to ensure that a transmission system of the type described above will attain neutral under various operating conditions, such as power upshifts, power downshifts, coasting downshifts, coasting downshifts with engine brake actuation, cold weather, hot weather, etc.
2. Description of the Prior Art
Fully and partially automated mechanical transmission systems intended for vehicular use are well known in the prior art, as may be seen by reference to U.S. Pat. Nos. 4,361,060; 4,648,290; 4,595,986; 4,850,236; 5,053,959; 5,109,721; 5,261,288; 5,315,218 and 5,335,566, the disclosures of which are incorporated herein by reference. In these types of systems, engine fueling/braking control is typically utilized to achieve synchronous conditions for engaging a target gear ratio.
The prior art automated transmission systems typically utilized electric, electro-mechanical, electro-hydraulic or electro-pneumatic type actuators to operate a plurality of generally parallel shift rails or a single shift shaft mechanism, or the like, through an X-Y mechanism and/or a plurality of linear actuators. Axially movable jaw clutch members are selectively axially positioned by shift yokes (also called shift forks) carried by shift shafts or block mechanisms, which are axially positioned by shift fingers, pistons and the like. Shift mechanisms of this type may be seen by reference to U.S. Pat. Nos. 4,445,393; 4,873,881; 4,899,607; 4,920,815; Re. 34,260; 4,945,484; 5,000,060; 5,052,535; 4,964,313 and 5,368,145, the disclosures of which are incorporated herein by reference.
It also is known in the prior art to provide automated mechanical transmission systems not having automated master clutch controls or other torque-interrupt devices and, thus, requiring controlled engine fueling to cause zero torque conditions for disengaging the jaw clutch members associated with a ratio to be disengaged. Examples of such automated transmission systems may be seen by reference to U.S. Pat. Nos. 4,722,248; 4,850,236 and 5,261,298, the disclosures of which are incorporated herein by reference.
The prior art controls for disengaging the jaw clutch members of the positive jaw clutch associated with a ratio to be disengaged in a system not having an automated torque-interrupt device, such as an automated master clutch, were not totally satisfactory, as such controls were not sufficiently robust to ensure that the transmission will attain neutral under a wide variety of operating conditions, especially in those systems not equipped with means to sense and/or determine current drivetrain torque values and/or required changes in engine fueling of an undesirably large magnitude.